Vibrational relaxation of triplet chlorotoulenes studied by photosensitized phosphorescence of biacetyl

The photosensitized phosphorescence of biacetyl by chlorotoulene vapors has been investigated under stationary conditions. Quantum yields of stable triplet formation for chlorotoulenes increased with increasing foreign gas (ethane) pressure, suggesting that vibrational relaxation of initially formed triplet levels is competitive with photodissociation of the CCl bond. Foreign-gas pressure effects on the triplet formation yield by the 0-0 excitation has lead to photodecomposition rate constants of chlorotoluenes ( ≈ 10² s^?1). Step-ladder collisional relaxation processes have been postulated for the excitation at shorter wavelengths.